1. Field of the Invention
The present invention relates to a damper installed in a drum type washing machine for supporting a tub as well as absorbing vibration of the tub, and more particularly to a damper for use in drum type washing machines, which prevents generation of rubbing and collision of a tub even in case of multi-directional vibration, resulting in an enhancement in reliability thereof.
2. Description of the Related Art
In general, a drum type washing machine comprises a drum horizontally installed therein for loading the laundry, washing water and detergent, and is adapted to perform washing of the laundry by making use of friction between the laundry and the drum as the drum is rotated by the driving force of a motor. Such a drum type washing machine almost never causes damage or tangling of the laundry, and provides good washing effects of the same quality as if the laundry were washed by hand.
The drum type washing machine further comprises a tub in which the drum is rotatably installed, and behind the tub is installed the motor so as to be connected to the drum of the tub.
In an installed state, an upper end of the tub is suspended within a cabinet, which defines an external appearance of the washing machine, by means of a pair of springs, and a lower end of the tub is supported on a base, formed as a bottom portion of the cabinet, by means of a pair of dampers. The springs are installed at both lateral positions on the upper end of the tub, and the dampers are installed at both lateral positions on the lower end of the tub.
With the construction as stated above, vibration, caused in the drum as the drum is rotated by the motor, is mostly absorbed by the springs and dampers as it is transmitted to the cabinet and base by passing through the tub.
FIG. 1 is a side sectional view illustrating a damper for use in a drum type washing machine in accordance with the prior art, and FIG. 2 is a side sectional view illustrating a state wherein non-axial load is applied to the damper for use in a drum type washing machine in accordance with the prior art.
As shown in FIG. 1, the conventional damper for use in a drum type washing machine, designated as reference numeral 10, comprises a cylinder 12 hingedly connected at an upper end thereof to the bottom of the tub, a piston 14 which is movably inserted from its upper end into a lower end of the cylinder 12 and is hingedly connected at its lower end to an upper surface of the base, a guide portion 16 extending from the upper end of the piston 14, a fixed damping member 18 which is fixed around an outer peripheral surface of the upper end of the piston 14 and is adapted to frictionally move along an inner peripheral surface of the cylinder 12, and a movable damping member 19 which is installed around the guide portion 16 in an axially movable manner and is adapted to frictionally move along the inner peripheral surface of the cylinder 12.
In this case, excessive vibration caused between the cylinder 12 and piston 14 may cause the movable damping member 19 to be unintentionally separated from the piston 14. In order to solve this problem, a stopper 16a radially protrudes from an upper end of the guide portion 16.
By virtue of the fixed damping member 18 and movable damping member 19 coming into close contact with the cylinder 12, when the piston 14 and cylinder 12 move relative to each other due to the vibration of the tub, the piston 14 frictionally moves inside the cylinder 12, thereby serving to attenuate the vibration of the tub.
In a normal state wherein the motor is driven at a constant speed, resulting in a relatively low production of vibration of the tub, only the fixed damping member 18 frictionally moves along the inner peripheral surface of the cylinder 12 so as to attenuate the vibration of the tub. In an inordinate state wherein the motor is driven at excessively high or low speed, resulting in a relatively large production of vibration of the tub, both the fixed damping member 18 and movable damping member 19 frictionally move together along the inner peripheral surface of the cylinder 12 so as to attenuate the vibration of the tub.
The movable damping member 19 is designed to produce a damping force greater than or equal to that of the fixed damping member 18.
Although the conventional damper 10 for use in a drum type washing machine can smoothly attenuate the vibration of the tub by means of the fixed damping member 18 and movable damping member 19 when the piston 14 moves relative to the cylinder 12 in an axial direction, if the tub vibrates in a non-axial direction of the damper 10, as shown in FIG. 2, it results in rubbing and collision of the piston 14 with cylinder 12.
As will be easily understood, a distance between the fixed damping member 18 and movable damping member 19 is variable during the axial relative movements of the piston 14 and cylinder 12. When the distance between the fixed damping member 18 and movable damping member 19 reaches the minimum, especially, if the tub vibrates in a non-axial direction of the damper 10, the piston 14 and cylinder 12 rotate relative to each other in an angular direction, and thus the piston 14 is inclined relative to the cylinder 12. This generates interference between the cylinder 12 and piston 14, thereby causing the lower end of the cylinder 12 to collide with the piston 14.
Such a relative angular rotation of the cylinder 12 and piston 14, further, results in the torsion of the fixed damping member 18 and movable damping member 19. This causes a contact force between the damping members 18 and 19 and the cylinder 12 to be varied depending on positions, and reduces a contact area therebetween, resulting in deterioration in damping performance of the damper 10.
In addition to the above problems, the conventional damper 10 has several problems including damage to constituent components due to the rubbing and collision of the cylinder 12 and piston 14, and periodic generation of noise due to the vibration of the tub, resulting in deterioration in reliability of products.